I just noticed that I am unable to add the CombinedFragment to my
diagram. I tried with the "loop" and "seq".
Eclipse stack trace is:

org.eclipse.core.commands.ExecutionException: While executing the operation, an exception occurred
at org.eclipse.core.commands.operations.DefaultOperationHistory .execute(DefaultOperationHistory.java:519)
at org.eclipse.gmf.runtime.diagram.ui.parts.DiagramCommandStack .execute(DiagramCommandStack.java:206)
at org.eclipse.gmf.runtime.diagram.ui.parts.DiagramCommandStack .execute(DiagramCommandStack.java:169)
at org.eclipse.gmf.runtime.diagram.ui.parts.DiagramCommandStack .execute(DiagramCommandStack.java:156)
at org.eclipse.gef.tools.AbstractTool.executeCommand(AbstractTo ol.java:399)
at org.eclipse.gef.tools.AbstractTool.executeCurrentCommand(Abs tractTool.java:411)
at org.eclipse.gmf.runtime.diagram.ui.tools.CreationTool.perfor mCreation(CreationTool.java:133)
at org.eclipse.gef.tools.CreationTool.handleButtonUp(CreationTo ol.java:178)
at org.eclipse.gef.tools.AbstractTool.mouseUp(AbstractTool.java :1064)
at org.eclipse.gef.EditDomain.mouseUp(EditDomain.java:263)
at org.eclipse.gef.ui.parts.DomainEventDispatcher.dispatchMouse Released(DomainEventDispatcher.java:374)
at org.eclipse.draw2d.LightweightSystem$EventHandler.mouseUp(Li ghtweightSystem.java:538)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListe ner.java:207)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java :84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.ja va:3880)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java :3473)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.jav a:2405)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2369)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:22 21)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:500)
at org.eclipse.core.databinding.observable.Realm.runWithDefault (Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Work bench.java:493)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.j ava:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start (IDEApplication.java:113)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(Eclips eAppHandle.java:194)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher .runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher .start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseS tarter.java:368)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseS tarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java: 559)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
at org.eclipse.equinox.launcher.Main.run(Main.java:1311)
Caused by: java.lang.NullPointerException
at org.eclipse.uml2.diagram.sequence.model.edit.CreateCombinedF ragment.createCombinedFragment(CreateCombinedFragment.java:3 6)
at org.eclipse.uml2.diagram.sequence.edit.create.CreateCombined FragmentEditPolicy$1.doExecuteWithResult(CreateCombinedFragm entEditPolicy.java:125)
at org.eclipse.gmf.runtime.emf.commands.core.command.AbstractTr ansactionalCommand.doExecute(AbstractTransactionalCommand.ja va:247)
at org.eclipse.emf.workspace.AbstractEMFOperation.execute(Abstr actEMFOperation.java:150)
at org.eclipse.emf.workspace.CompositeEMFOperation.doExecute(Co mpositeEMFOperation.java:217)
at org.eclipse.emf.workspace.AbstractEMFOperation.execute(Abstr actEMFOperation.java:150)
at org.eclipse.gmf.runtime.common.core.command.CompositeCommand .doExecuteWithResult(CompositeCommand.java:403)
at org.eclipse.gmf.runtime.common.core.command.AbstractCommand. execute(AbstractCommand.java:135)
at org.eclipse.gmf.runtime.common.core.command.CompositeCommand .doExecuteWithResult(CompositeCommand.java:403)
at org.eclipse.gmf.runtime.common.core.command.AbstractCommand. execute(AbstractCommand.java:135)
at org.eclipse.core.commands.operations.DefaultOperationHistory .execute(DefaultOperationHistory.java:511)
... 36 more

Does this indicate a bug? Or is it a problem with my setup? Should I attach my model and .umlseq?